So to needlessly simplify it, deuterium in a warp reactor is sort of analogous to water in a steam engine, in that it's a necessity for efficient matter-antimatter reactions, but it's easy to obtain and use compared to antimatter or dilithium.

I found a YouTube link in your post. Here are links to the same video on alternative frontends that protect your privacy:

• yewtu.be
• inv.nadeko.net
• yt.artemislena.eu
• piped.video